Agricultural implements can be attached to a three point hitch of an agricultural tractor. A three point hitch normally includes a draft sensing mechanism which provides a draft force signal to a control system which lowers and raises the implement as a function of sensed draft force and possibly as a function of other sensed parameters, such as position, engine speed, wheel slip, etc. Some known production draft sensing mechanisms have a number of moving parts that require periodic maintenance. This includes removing mud and dirt accumulation and lubricating a draft sensor plunger to prevent moisture and dirt contamination. In certain conditions, accumulated dirt and mud can prevent the required component movement and can causes false draft force signals. Future tractor designs will have less room for such draft sensor components. Thus, it is desired to have a draft sensor which requires less space, which has no moving parts requiring lubrication and which does not need to be protected from dirt accumulation.
Other known a draft sensing mechanisms have required costly draft sensing pins, bending bars, and draft sensing shafts. Draft sensing pins require two instrument pins which double the cost and decrease the reliability. Certain current draft sensing system on John Deere four wheel drive tractors measures the deflections of the draft link mount straps. These straps are large and a large number of parts are required to measure this signal. The system also has moving parts. The bending bar and draft sensing shaft systems have moving parts and require a sealed compartment and a fair amount of space. A simpler, lower cost and more reliable draft sensing mechanism is desired.